Pip prepares for his new life in London.What, in regards to Joe, does Pip request of Biddy once he leaves and why?

Pip asks Biddy if she would try and educate Joe so that he could bring him up to another social level once the full extent of Pip's sponsor's fortune is given to him. Pip is being egotistical and pompous in assuming other people in his life need to rise up in class as he will.